The idea of classified discussion is to analyze and solve different situations according to the nature differences of the studied objects. Mathematical problems related to classified discussion are obviously logical, comprehensive and exploratory. At the same time, classified discussion questions cover more knowledge points, which is conducive to examining students' knowledge and requires higher ability, so they have always occupied an important position in the college entrance examination. The key to solving mathematical problems by using classification discussion method is how to classify correctly. In other words, correctly choose a classification standard to ensure the scientificity, non-repetition, non-omission and unification of classification. This paper puts forward some views on how to determine the classification standard of classification discussion through specific examples for reference. Some mathematical concepts limit the research scope when they are defined, such as the intercept equation of a straight line; However, some mathematical concepts must meet certain conditions before they can be established, such as the solution of a quadratic equation. To solve the above problems, we must classify them conceptually. Example l] (Liaoning Volume of College Entrance Examination in L](06) It is known that the function f(x) is one (5 1 one+). .